Clinical impact of portal vein pulsatility on the prognosis of hospitalized patients with acute heart failure

BACKGROUND

Heart failure (HF) causes extracardiac organ congestion, including in the hepatic portal system. Reducing venous congestion is essential for HF treatment, but evaluating venous congestion is sometimes difficult in patients with chronic HF. The portal vein (PV) flow pattern can be influenced by right atrial pressure. Ultrasound images of the PV are quite easy to obtain and are reproducible among sonographers. However, the association between PV pulsatility and the condition of HF remains unclear. We hypothesize that PV pulsatility at discharge reflects the condition of HF.

AIM

To evaluate the usefulness of PV pulsatility as a prognostic marker for hospitalized patients with acute HF.

METHODS

This observational study was conducted from April 2016 to January 2017 and April 2018 to April 2019 at Shinko Hospital. We enrolled 56 patients with acute HF, and 17 patients without HF served as controls. PV flow velocity was measured by ultrasonography on admission and at discharge. We calculated the PV pulsatility ratio (PVPR) as the ratio of the difference between the peak and minimum velocity to the peak velocity. The primary endpoint was cardiac death and HF re-hospitalization. The observation period was 1 year from the first hospitalization. The Kaplan-Meier method was used to determine the stratified composite event-free rates, and the log-rank test was used for comparisons between groups.

RESULTS

On admission, the PVPR was significantly higher in patients with acute HF than controls (HF: 0.29 ± 0.20 vs controls: 0.08 ± 0.07, P < 0.01). However, the PVPR was significantly decreased after the improvement in HF (admission: 0.29 ± 0.20 vs discharge: 0.18 ± 0.15, P < 0.01) due to the increase in minimum velocity (admission: 12.6 ± 4.5 vs discharge: 14.6 ± 4.6 cm/s, P = 0.03). To elucidate the association between the PVPR and cardiovascular outcomes, the patients were divided into three groups according to the PVPR tertile at discharge (PVPR-T1: 0 ≤ PVPR ≤ 0.08, PVPR-T2: 0.08 < PVPR ≤ 0.21, PVPR-T3: PVPR > 0.21). The Kaplan-Meier analysis showed that patients with a higher PVPR at discharge had the worst prognosis among the groups.

CONCLUSION

PVPR at discharge reflects the condition of HF. It is also a novel prognostic marker for hospitalized patients with acute HF.

Impact of radial compression protocols on radial artery occlusion and hemostasis time in coronary angiography

Protocols for hemostasis after trans-radial approach (TRA) vary depending on the institute as there is no established evidence-based protocol. This study aimed to investigate the clinical implications of radial compression protocols. Consecutive patients who underwent outpatient invasive catheter angiography before and after April 2018 were treated with traditional and new protocols, respectively. Using the same hemostasis band, in the conventional protocol, fixed amount of air was removed soon after the procedure, 2 h later, and 3 h later, whereas the air was removed as much as possible every 30 min in the new protocol. A total of 1842 patients (71 ± 10 years old, 77% male) were included. Compared with the traditional protocol group (n = 1001), the new protocol group (n = 841) had a significantly lower rate of dual antiplatelet therapy (35% and 24% in the traditional and new groups, respectively, p < 0.001). The time required for complete hemostasis was approximately one-third with the new protocol (190 ± 16 and 66 ± 32 min, p < 0.001) with no clinically relevant bleeding. The incidence of radial artery occlusion (RAO) was 9.8% and 0.9% in the traditional and new protocol groups, respectively (p < 0.001). After adjusting for covariates, the new protocol was associated with a reduced risk of RAO (odds ratio 0.10, p < 0.001) and a shorter hemostasis time (odds ratio 0.01, p < 0.001). The new protocol for hemostasis after TRA was strongly associated with a shorter hemostasis time and a lower rate of RAO.

Impact of radial compression protocols on the compression time and radial artery occlusion

Background

Trans-radial access (TRA) has been established as a safe and established approach for invasive coronary catheter procedures. However, protocols for post-procedural hemostasis varies depending on institutes and an evidence-based protocol is lacking.

Purpose

The objective of this study was to investigate the clinical implications of procedural hemostasis.

Methods

Consecutive patients who were referred to outpatient catheter examination before and after April 2018 were treated with an old and a new protocol, respectively. In both protocols, we used the same commercially available hemostasis band with injecting an air of 16 ml for hemostasis. In the old protocol, the amount and timing of deflation were fixed, whereas the air was removed as much as possible for every 30 minutes in the new protocol. Time to complete hemostasis, the rate of major bleeding, and the rate of radial artery occlusion (RAO) at 6 months after the catheter examination were compared between the protocols.

Results

Total of 1,843 (71±10 years old, 77% male) patients was included in the study. Between patients in the old and the new protocol group (n=1,000 and 843, respectively), there was no significant difference in age, gender, body size, or systolic blood pressure. The new group had significantly higher prevalence of diabetes (47% vs 39%, p=0.002), slightly larger sheath size (4.1±0.3 vs 4.0±0.2 Fr, p&lt;0.001), and lower rate of dual antiplatelet therapy (DAPT: 24% vs. 35%, p&lt;0.001). Time for complete hemostasis was about one-third with the new protocol compared with the old protocol (65±32 vs. 190±16 min, p&lt;0.001) and there was no major bleeding in either group. The rate of radial artery occlusion was 0.7% and 9.8% in the old and the new group (p&lt;0.001). Multivariate analysis showed that the significant predictor of prolonged hemostasis time were the old protocol (odds ratio: OR 80.5, p&lt;0.001) and the prescription of DAPT (OR 2.9, p&lt;0.001), while the factors associated with higher risk of radial occlusion were the old protocol (OR 13.9, p&lt;0.001), the number of previous TRA (OR 1.1, p&lt;0.001), and smaller body size (OR 0.127 per 1 m2 increase p=0.005).

Conclusions

Our new protocol for hemostasis after TRA was strongly associated with shorter hemostasis time and a lower rate of radial artery occlusion. This approach will decrease the post-procedural hospital time with even fewer complication rates.

Study outline

Funding Acknowledgement

Type of funding source: None

Recurrent myocardial infarction associated with vasculo-Behçet's disease: a case report

A 39-year-old Japanese man presented with chest oppression in February 2017. Electrocardiogram showed ST-elevation myocardial infarction (MI), and cardiac catheterisation revealed thrombotic occlusion of the right coronary artery (RCA), which was treated with thrombectomy, and he received warfarin. Three days after discharge, he complained of chest oppression again, and re-cardiac catheterisation showed thrombi occlusion of the circumflex artery (LCX) and 90% stenosis with thrombosis in the proximal site of the anterior descending artery (LAD) and RCA. Drug eluting stent was implanted in the LAD and RCA; aspirin and prasugrel hydrochloride were added to warfarin. Before discharge, coronary computed tomography angiography (CTA) found new thrombi in the RCA, LAD, and LCX, and he was referred to our hospital on suspicion of Behçet's disease (BD). Past medical history was notable for recurrent aphthous stomatitis, a pudendal ulcer, and Crohn's disease, for which he had been taking infliximab (5 mg/kg) every 8 weeks until December 2016. Notably, his C-reactive protein (CRP) level increased before and after each MI, suggesting that the thrombi were caused by inflammation. Consequently, we concluded that his abnormalities were manifestations of vasculo-BD. After 3 days of hospitalisation, treatment with prednisolone and colchicine was started. His CRP and D-dimer levels decreased, and coronary CTA after 8 days showed disappearance of the thrombi. We tapered the prednisolone dose, and cardiovascular events have not been observed for 7 months after the treatment initiation. In summary, we report a rare case of MI associated with vasculo-BD and review the relevant literature.

An Unusual Case of Inferior Vena Cava Thrombosis in a Healthy Male Bodybuilder

Inferior vena cava (IVC) thrombosis is very rare, particularly in the absence of an apparent congenital caval abnormality or hypercoagulable state. We herein report an unusual case of a healthy and active 62-year-old male bodybuilder with a mass-like IVC thrombus. We placed an IVC filter and began treatment with rivaroxaban. The patient recovered successfully, and the IVC thrombus completely disappeared three months later. This case suggested that extrinsic compression of IVC by a tightened weightlifting belt around the abdomen is a triggering factor of IVC thrombosis, and rivaroxaban, a new oral anticoagulant, may be a useful option for treatment.

Acute pulmonary edema in patients with reduced left ventricular ejection fraction is associated with concentric left ventricular geometry

Although acute pulmonary edema (APE) is common in patients with heart failure (HF) with preserved ejection fraction (EF), its pathogenesis in patients with HF with reduced EF (HFrEF) is not completely understood. The purpose of our study was to explore the contributions of left ventricular (LV) geometry to understand the difference between HFrEF patients with or without APE. We studied 122 consecutive acute decompensated HF patients with HFrEF (≤40%). APE was defined as acute-onset dyspnea and radiographic alveolar edema requiring immediate airway intervention. LV geometry was determined from a combination of the LV mass index and relative wall thickness (RWT). Long-term unfavorable outcome events were tracked during a follow-up of a median of 21 months (interquartile range, 10-28 months), during which APE was observed in 29 patients (24%). Compared to those without APE, hospitalized patients with APE had a higher systolic blood pressure, RWT, and LVEF and lower end-diastolic dimension. Among echocardiographic variables, a multivariate logistic regression analysis identified RWT as the only independent determinant of APE (hazard ratio: 2.46, p < 0.001). Those with concentric geometry (n = 25; RWT > 0.42) had a higher incidence of APE relative to those with non-concentric geometry. Furthermore, among patients with APE, mortality was significantly higher among those with concentric geometry (log-rank, p = 0.008). Compared with non-concentric geometry, concentric geometry (increased RWT, not LV mass) was strongly associated with APE onset and a poorer outcome among APE patients. An easily obtained echocardiographic RWT index may facilitate the risk stratification of patients.

[An Elderly Patient with Local Recurrence of Gastric Cancer Responding Completely to S-1 Monotherapy]

An 80-year-old man with a local recurrence of gastric cancer was treated with S-1 monotherapy leading to a complete response(CR).The patient was diagnosed with gastric cancer and underwent a distal gastrectomy with lymph node dissection. Pathological findings showed tub2>por1, pT3 (SS), pN2, pStage III A.Five months after surgery, the patient presented with redness of the abdominal skin.Computed tomography (CT) revealed massive tumors in the abdominal cavity with invasion to the abdominal wall. He was administered S-1, 80 mg/body/day for 14 days, followed by a 7-day rest.After 2 courses of treatment, CT showed a dramatic reduction of the tumors. After 6 months, the tumor tissue completely disappeared and he had a CR.Administration of S-1 was continued for 2 years and 6 months.There was no relapse for 3 years after discontinuation.S -1 monotherapy appears to be a feasible and effective therapy for elderly patients with recurrent gastric cancer.

Direct correlationship between proton translocation and growth yield: an analysis of the respiratory chain of Bacillus stearothermophilus

Thermophilic bacilli contain cytochrome caa3-type cytochrome c oxidase as the main terminal oxidase in the respiratory chain. A mutant strain, named K-17, lacking cytochrome caa3 and exhibiting very low N,N,N',N'-tetramethyl-p-phenylene diamine oxidase activity, was isolated by random mutation from Bacillus stearothermophilus K1041 (Sakamoto, J. et al., FEMS Microbiol. Lett., 143, 151-158, 1996). Comparing this mutant with the parent strain K1041, we observed the following differences in energy-yielding properties. (i) K-17 gave an cell yield less than one half of that of the wild type, although the doubling time of K-17 was only a little slower than that of the parent strain. (ii) In cellular respiration, the H+/O ratio of K-17 was 2.9-3.1, while that of the wild type was 6.1-6.5. (iii) A low concentration of cyanide inhibited endogenous respiration of the wild-type cells partly with a concomitant reduction of the H+/O ratio to around 3, while it did not significantly affect the respiration rate and the H+/O ratio of the K-17 cells. (iv) Cytochrome bd-type quinol oxidase seemed to operate in the wild-type cells when a low concentration (below 0.5 mM) of cyanide was added, while this enzyme is the main terminal oxidase in K-17. The K-17 cells also contained cytochrome b(o/a)3-type cytochrome c-551 oxidase. These results demonstrated that the combination of the enzymes involved in the respiratory chain determines the H+/O ratios of the cell and consequently the growth yield of the bacteria.

Inhibitory activities of lansoprazole against respiration in Helicobacter pylori

Lansoprazole and its derivative AG-1789 dose-dependently inhibited cellular respiration by an endogenous substrate and decreased the ATP level in Helicobacter pylori cells. The inhibitory action of lansoprazole and AG-1789 against respiration was specific to substrates such as pyruvate and alpha-ketoglutarate and similar to the inhibitory action of rotenone, which is an inhibitor for the mitochondrial respiratory chain. Growth inhibition by lansoprazole and AG-1789 as well as by rotenone was augmented at high oxygen concentrations under atmospheric conditions. Since the 50% inhibitory concentrations of these compounds for the respiration were close to their MICs for H. pylori growth, the growth inhibition might be due to respiratory inhibition by these compounds.

A novel hydrophobic diheme c-type cytochrome. Purification from Corynebacterium glutamicum and analysis of the QcrCBA operon encoding three subunit proteins of a putative cytochrome reductase complex

Electrophoresis of a Corynebacterium glutamicum membrane preparation in the presence of sodium dodecyl sulfate, followed by staining for peroxidase activity (heme staining), showed only one band at about 28 kDa. This 28 kDa protein was purified from C. glutamicum membranes by chromatography in the presence of decylglucoside using DEAE-Toyopearl and hydroxylapatite columns, as the sole c-type cytochrome in the bacterium. The cytochrome showed an alpha band at 551 nm, and its E(m, 7) was about 210 mV. A QcrCAB operon encoding the subunits of a putative quinol cytochrome c reductase was found 3'-downstream of ctaE encoding subunit III of cytochrome aa(3) in the C. glutamicum genome. The deduced amino acid sequence of qcrC, composed of 283 amino acid residues, contained two heme C-binding motifs and was in agreement with partial peptide sequences obtained from the 28 kDa protein after V8 protease digestion. We propose to name this protein cytochrome cc. The presence of cytochrome cc is a common feature of high G+C content Gram-positive bacteria, since we could confirm this protein by electrophoresis; homologous QcrCAB operons are also known in Mycobacterium and Streptomyces. QcrA and qcrB of C. glutamicum encode the Rieske Fe-S protein and cytochrome b, respectively, although these proteins were not co-purified with cytochrome cc. The phylogenetic tree of cytochromes b and b(6) show that C. glutamicum cytochrome b, along with those of other bacteria in the high G+C group, is rather different from the Bacillus counterparts, but highly similar to the Deinococci and Thermus cytochromes. This indicates that there is a fourth group of bacteria in addition to the three clades: proteobacterial cytochrome b, cyanobacterial b(6) and green sulfur-low G+C Gram-positive bacteria.

Active site structure of SoxB-type cytochrome bo3 oxidase from thermophilic Bacillus

Two-subunit SoxB-type cytochrome c oxidase in Bacillus stearothermophilus was over-produced, purified, and examined for its active site structures by electron paramagnetic resonance (EPR) and resonance Raman (RR) spectroscopies. This is cytochrome bo3 oxidase containing heme B at the low-spin heme site and heme O at the high-spin heme site of the binuclear center. EPR spectra of the enzyme in the oxidized form indicated that structures of the high-spin heme O and the low-spin heme B were similar to those of SoxM-type oxidases based on the signals at g=6.1, and g=3.04. However, the EPR signals from the CuA center and the integer spin system at the binuclear center showed slight differences. RR spectra of the oxidized form showed that heme O was in a 6-coordinated high-spin (nu3 = 1472 cm(-1)), and heme B was in a 6-coordinated low-spin (nu3 = 1500 cm(-1)) state. The Fe2+-His stretching mode was observed at 211 cm(-1), indicating that the Fe2+-His bond strength is not so much different from those of SoxM-type oxidases. On the contrary, both the Fe2+-CO stretching and Fe2+-C-O bending modes differed distinctly from those of SoxM-type enzymes, suggesting some differences in the coordination geometry and the protein structure in the proximity of bound CO in cytochrome bo3 from those of SoxM-type enzymes.

Purification and characterization of cytochrome c-553 from Helicobacter pylori

Helicobacter pylori, a microaerophilic Gram-negative spiral bacterium residing in the human stomach, contains a small size soluble cytochrome c. This cytochrome c was purified from the soluble fraction of H. pylori by conventional chromatographies involving octyl-cellulose and CM-Toyopearl. Its reduced form gave an alpha absorption band at 553 nm, and thus the cytochrome was named H. pylori cytochrome c-553. The cytochrome, giving a band below 10,000 Da upon SDS-PAGE, was determined to have a mass of 8,998 by time of flight mass spectroscopy. Its N-terminal peptide sequence was TDVKALAKS---, indicating that the nascent polypeptide was cleaved to produce a signal peptide of 19 amino acid residues and a mature protein composed of 77 amino acid residues. The cb-type cytochrome c oxidase oxidized ferrocytochrome c-553 of this bacterium actively (V(max) of about 250 s(-1)) with a small K(m) (0.9 microM). Analysis of the effect of the salt concentration on the oxidase activity indicated that oxidation of cytochrome c-553 is highly inhibited under high ionic conditions. The amino acid sequence of H. pylori cytochrome c-553 showed the closest similarity to that of Desulfovibrio vulgaris cytochrome c-553, and these sequences showed a weak relationship to that of the cytochrome c(8)-group among class I cytochromes c.

Menaquinol oxidase activity and primary structure of cytochrome bd from the amino-acid fermenting bacterium Corynebacterium glutamicum

Cytochrome d was spectroscopically detected in membrane fractions of the amino-acid-fermenting, high-G+C gram-positive bacterium Corynebacterium glutamicum. Inhibition of NADH oxidase activity in the membranes by cyanide suggested that the main terminal respiratory oxidase during the stationary phase was a type of cytochrome bd. Cytochrome bd-type quinol oxidase, purified from the membranes, was composed of two subunits. Its reduced form showed absorption peaks at 627, 595, and 560 nm, which were due to haem d, high-spin protohaem, and low-spin protohaem, respectively. The air-oxidised form showed a peak at 645 nm, which might be due to oxygenated ferrous haem d. The spectral features and the size of subunit I are more similar to the properties of cytochromes bd from Proteobacteria, such as Escherichia coli, than to those of cytochrome bd from low-G+C gram-positive bacteria, such as Bacillus stearothermophilus. The menaquinol oxidase activity of the purified cytochrome bd was low, but was enhanced about fivefold by pre-incubating the enzyme with menaquinones. The order of effectiveness of quinols as oxidase substrates was clearly different from that of quinones as the activators of enzyme activity. Furthermore, activation was destroyed by ultraviolet irradiation of the pre-incubated enzyme and then restored by a second incubation with menaquinone. These results indicate that the enzymatic properties of this new oxidase are more similar to the properties of cytochromes bd from low-G+C gram-positive bacterial than to those of proteobacterial counterparts. They also suggest that the enzyme has a second quinone-binding site essential for full activity, in addition to the active centre for substrate oxidation. By using probes based on partial peptide sequences of the subunits, the genes for the two subunits of C. glutamicum cytochrome bd were cloned. The deduced amino acid sequence demonstrated that subunit I lacks the C-terminal half of the Q loop and that the primary structure of C. glutamicum cytochrome bd is more similar to that of other gram-positive bacteria than to proteobacterial cytochromes bd.

Energy-yielding properties of SoxB-type cytochrome bo(3) terminal oxidase: analyses involving Bacillus stearothermophilus K1041 and its mutant strains

We isolated a K17q8 mutant from K17 mutant cells of Bacillus stearothermophilus which contain SoxB-type cytochrome bo(3) as well as cytochrome bd but not SoxM-type cytochrome caa(3), which is the main terminal oxidase in B. stearothermophilus K1041. The respiration of K17q8 was highly sensitive to as little as 10 microM cyanide, indicating that the main terminal oxidase is cytochrome bo(3). The aerobic growth yield of K17q8 was lower than that of wild-type K1041, but higher than that of parental K17. The H(+)/O ratio of K17q8 was about 5, i.e. a little lower than the 6.1-6.5 of K1041, but higher than the 2.9-3.1 of K17 [Sone et al. (1999) J. Biosci. Bioeng. 87, 495-499]. Analyses of membrane fragments indicated that K17q8 contains about 0.2 nmol cytochrome bo(3) per mg membrane protein, and scarcely any subunits of cytochromes caa(3) and bd. From the membrane fraction of K17q8, cytochrome bo(3) was purified and shown to be composed of two subunits with apparent molecular masses of 56 and 19 kDa. The enzyme contained protoheme IX and heme O, as the main low-spin heme and high-spin heme. Analysis of the substrate specificity indicated that the high-affinity site is very specific to cytochrome c-551, a cytochrome c which is a membrane-bound lipoprotein of thermophilic Bacillus. The I(50) of purified cytochrome bo(3) was determined to be 4 microM, indicating that cytochrome bo(3) among the three terminal oxidases in B. stearothermophilus was most susceptible to cyanide. The respiration of K17q8 was mostly inhibited by the addition of cyanide at this concentration.

Over-expression of cbaAB genes of Bacillus stearothermophilus produces a two-subunit SoxB-type cytochrome c oxidase with proton pumping activity

We constructed expression plasmids containing cbaAB, the structural genes for the two-subunit cytochrome bo(3)-type cytochrome c oxidase (SoxB type) recently isolated from a Gram-positive thermophile Bacillus stearothermophilus. B. stearothermophilus cells transformed with the plasmids over-expressed an enzymatically active bo(3)-type cytochrome c oxidase protein composed of the two subunits, while the transformed Escherichia coli cells produced an inactive protein composed of subunit I without subunit II. The oxidase over-expressed in B. stearothermophilus was solubilized and purified. The oxidase contained protoheme IX and heme O, as the main low-spin heme and the high-spin heme, respectively. Analysis of the substrate specificity indicated that the high-affinity site is very specific for cytochrome c-551, a cytochrome c that is a membrane-bound lipoprotein of thermophilic Bacillus. The purified enzyme reconstituted into liposomal vesicles with cytochrome c-551 showed H(+) pumping activity, although the efficiency was lower than those of cytochrome aa(3)-type oxidases belonging to the SoxM-type.

Reduced immunogenicity of beta-lactoglobulin by conjugation with carboxymethyl dextran

We prepared two beta-lactoglobulin (beta-LG)-carboxymethyl dextran (CMD) conjugates (Conj. 10A and Conj. 10B) by using a water-soluble carbodiimide to decrease the immunogenicity of beta-LG. The molar ratios of beta-LG to CMD in the conjugates were 5:1 (Conj. 10A) and 2:1 (Conj. 10B). The beta-LG-CMD conjugates maintained the retinol-binding activity of native beta-LG. Intrinsic fluorescence study indicated that shielding of the surface of beta-LG by CMD occurred in each conjugate, which was eminent in Conj. 10B. A local conformational change around (125)Thr-(135)Lys (alpha-helix) in each conjugate was detected by ELISA with monoclonal antibodies. The denaturation temperature of beta-LG evaluated by differential scanning calorimetry was greatly enhanced in each conjugate. The anti-beta-LG antibody response was markedly reduced after immunization with the beta-LG-CMD conjugates in BALB/c, C57BL/6, and C3H/He mice. We determined the B cell epitopes of beta-LG and each conjugate recognized in these mice and found that the linear epitope profiles of the beta-LG-CMD conjugates were similar to those of beta-LG, while the antibody response for each epitope was dramatically reduced. The reduced immunogenicity of beta-LG was most marked in the case of Conj. 10B, which contained more CMD than Conj. 10A, and was effectively shielded by CMD. We concluded that masking of epitopes by CMD is responsible for the decreased immunogenicity of the beta-LG in these conjugates.

Defining the structural domain of subunit II of the heme-copper terminal oxidase using chimeric enzymes constructed from the Escherichia coli bo-type ubiquinol oxidase and the thermophilic Bacillus caa(3)-type cytochrome c oxidase

To probe the location of the quinol oxidation site and physical interactions for inter-subunit electron transfer, we constructed and characterized two chimeric oxidases in which subunit II (CyoA) of cytochrome bo-type ubiquinol oxidase from Escherichia coli was replaced with the counterpart (CaaA) of caa(3)-type cytochrome c oxidase from thermophilic Bacillus PS3. In pHNchi5, the C-terminal hydrophilic domain except a connecting region as to transmembrane helix II of CyoA was replaced with the counterpart of CaaA, which carries the Cu(A) site and cytochrome c domain. The resultant chimeric oxidase was detected immunochemically and spectroscopically, and the turnover numbers for Q(1)H(2) (ubiquinol-1) and TMPD (N,N, N',N'-tetramethyl-p-phenylenediamine) oxidation were 28 and 8.5 s(-1), respectively. In pHNchi6, the chimeric oxidase was designed to carry a minimal region of the cupredoxin fold containing all the Cu(A) ligands, and showed enzymatic activities of 65 and 5.1 s(-1), and an expression level better than that of pHNchi5. Kinetic analyses proved that the apparent lower turnover of the chimeric enzyme by pHNchi6 was due to the higher K(m) of the enzyme for Q(1)H(2) (220 microM) than that of cytochrome bo (48 microM), while in the enzyme by pHNchi5, both substrate-binding and internal electron transfer were perturbed. These results suggest that the connecting region and the C-terminal alpha(1)-alpha(2)-beta(11)-alpha(3) domain of CyoA are involved in the quinol oxidation and/or physical interactions for inter-subunit electron transfer, supporting our previous proposal [Sato-Watanabe, M., Mogi, T., Miyoshi, H., and Anraku, Y. (1998) Biochemistry 37, 12744-12752]. The close relationship of E. coli quinol oxidases to cytochrome c oxidase of Gram-positive bacteria like Bacillus was also indicated.

Gene structure and quinol oxidase activity of a cytochrome bd-type oxidase from Bacillus stearothermophilus

Gram-positive thermophilic Bacillus species contain cytochrome caa3-type cytochrome c oxidase as their main terminal oxidase in the respiratory chain. We previously identified and purified an alternative oxidase, cytochrome bd-type quinol oxidase, from a mutant of Bacillus stearothermophilus defective in the caa3-type oxidase activity (J. Sakamoto et al., FEMS Microbiol. Lett. 143 (1996) 151-158). Compared with proteobacterial counterparts, B. stearothermophilus cytochrome bd showed lower molecular weights of the two subunits, shorter wavelength of alpha-band absorption maximum due to heme D, and lower quinol oxidase activity. Preincubation with menaquinone-2 enhanced the enzyme activity up to 40 times, suggesting that, besides the catalytic site, there is another quinone-binding site which largely affects the enzyme activity. In order to clarify the molecular basis of the differences of cytochromes bd between B. stearothermophilus and proteobacteria, the genes encoding for the B. stearothermophilus bd was cloned based on its partial peptide sequences. The gene for subunit I (cbdA) encodes 448 amino acid residues with a molecular weight of 50195 Da, which is 14 and 17% shorter than those of Escherichia coli and Azotobacter vinelandii, respectively, and CbdA lacks the C-terminal half of the long hydrophilic loop between the putative transmembrane segments V and VI (Q loop), which has been suggested to include the substrate quinone-binding site for the E. coli enzyme. The gene for subunit II (cbdB) encodes 342 residues with a molecular weight of 38992 Da. Homology search indicated that the B. stearothermophilus cbdAB has the highest sequence similarity to ythAB in B. subtilis genome rather than to cydAB, the first set of cytochrome bd genes identified in the genome. Sequence comparison of cytochromes bd and their homologs from various organisms demonstrates that the proteins can be classified into two subfamilies, a proteobacterial type including E. coli bd and a more widely distributed type including the B. stearothermophilus enzyme, suggesting that the latter type is evolutionarily older.

Cloning of Bacillus stearothermophilus ctaA and heme A synthesis with the CtaA protein produced in Escherichia coli

The Bacillus stearothermophilus ctaA gene, which is required for heme A synthesis, was found upstream of the ctaBCDEF/caaEABCD gene cluster as in B. subtilis and B. firmus. The deduced protein sequence indicate that CtaA is a 35-kDa intrinsic membrane protein with seven hydrophobic segments. Alignment of CtaA sequences showed conserved residues including histidines that may be involved in heme B binding and substrate binding. Expression of ctaA in E. coli resulted in increased formation of a membrane-bound b-type cytochrome, heme A production, and severe growth inhibition. Furthermore, B. stearothermophilus CtaA produced in E. coli was found to catalyze the conversion of heme O to heme A in vitro.

Characterization of a cb-type cytochrome c oxidase from Helicobacter pylori

Helicobacter pylori is a microaerophilic Gram-negative spiral bacterium residing in human stomach. A cb-type cytochrome c oxidase that terminates the respiratory chain was purified to near homogeneity by solubilizing the membranes with Triton X-100 and applying anion exchange, Cu-chelating, and gel filtration chromatographies. Redox- and CO-difference spectra and pyridine ferrohaemochrome analysis showed the enzyme to contain three haems C, one low-spin protohaem, and one high-spin protohaem that probably forms a dioxygen-reducing bimetalic center with a copper atom. The enzyme actively oxidizes soluble cytochrome c from this bacterium (TNmax of about 250 s-1) with a Km of 0.9 microM. Yeast cytochrome c and N,N,N',N'-tetramethyl p-phenylenediamine (TMPD) are also oxidized at similar maximal velocities with larger Km's. Oxygen pulse experiments on resting cells in the presence of ascorbate plus TMPD or L-lactate indicated that this sole terminal oxidase pumps H+, although the H+ pumping activity by proteoliposomes reconstituted from the enzyme and P-lipids was low. Two main bands with haem C at 58 and 26 kDa were observed upon polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and succeeding protein and haem staining. Sequencing of the operon encoding the subunits of the enzyme revealed the presence of ccoNOQP. N-terminal analysis of the 58 kDa band showed 15 or 13 amino acids coinciding with the amino acid sequences deduced from the DNA of ccoN and ccoO. CcoN, the largest subunit bearing two protohaems and copper, and ccoO, a mono-haem cytochrome subunit form a protein complex with an apparent molecular mass of 58 kDa, even in the presence of sodium dodecyl sulfate. The 26 kDa band is tentatively assumed to be ccoP with two haems C.

The cbaAB genes for bo3-type cytochrome c oxidase in Bacillus stearothermophilus

Structural genes were cloned for cytochrome bo3-type cytochrome c oxidase recently isolated from a Gram-positive thermophile Bacillus stearothermophilus. Sequencing and Northern blotting analyses indicated that the two genes cbaA and cbaB composed an operon encoding for subunits I and II, respectively, and that the oxidase was SoxB-type. They are the first genes for a SoxB-type cytochrome c oxidase whose natural substrate is known.

Did archaeal and bacterial cells arise independently from noncellular precursors? A hypothesis stating that the advent of membrane phospholipid with enantiomeric glycerophosphate backbones caused the separation of the two lines of descent

One of the most remarkable biochemical differences between the members of two domains Archaea and Bacteria is the stereochemistry of the glycerophosphate backbone of phospholipids, which are exclusively opposite. The enzyme responsible to the formation of Archaea-specific glycerophosphate was found to be NAD(P)-linked sn-glycerol-1-phosphate (G-1-P) dehydrogenase and it was first purified from Methanobacterium thermoautotrophicum cells and its gene was cloned. This structure gene named egsA (enantiomeric glycerophosphate synthase) consisted of 1,041 bp and coded the enzyme with 347 amino acid residues. The amino acid sequence deduced from the base sequence of the cloned gene (egsA) did not share any sequence similarity except for NAD-binding region with that of NAD(P)-linked sn-glycerol-3-phosphate (G-3-P) dehydrogenase of Escherichia coli which catalyzes the formation of G-3-P backbone of bacterial phospholipids, while the deduced protein sequence of the enzyme revealed some similarity with bacterial glycerol dehydrogenases. Because G-1-P dehydrogenase and G-3-P dehydrogenase would originate from different ancestor enzymes and it would be almost impossible to interchange stereospecificity of the enzymes, it seems likely that the stereostructure of membrane phospholipids of a cell must be maintained from the time of birth of the first cell. We propose here the hypothesis that Archaea and Bacteria were differentiated by the occurrence of cells enclosed by membranes of phospholipids with G-1-P and G-3-P as a backbone, respectively.

Characterization of two terminal oxidases in Bacillus brevis and efficiency of energy conservation of the respiratory chain

The respiratory chain of Bacillus brevis was analyzed. Resting cells showed an H+/O ratio of 4.8-5.2 (5.01+/-0.26), when measured using an oxygen pulse method with endogenous substrates. This value is intermediate between those of Bacillus subtilis (about 4), which predominantly expresses cytochrome aa3-type quinol oxidase, and Bacillus stearothermophilus (about 6), which has quinol cytochrome c reductase plus caa3-type cytochrome c oxidase. Measurement of respiration with various substrates, and its inhibition by cyanide suggested that aa3-type quinol oxidase and caa3-type cytochrome c oxidase operate simultaneously in the respiratory chain of B. brevis. Both terminal oxidases were isolated by solubilizing B. brevis membranes with Triton X-100, and fractionating the extract using DEAE-Fractgel and gel-filtration columns. The quinol oxidase (aa3) was composed of four subunits (57, 34, 23, and 15 kDa), like its counterpart of B. subtilis, while three subunits (52, 34, and 22 kDa) were identified in the cytochrome c oxidase (caa3) preparation in B. stearothermophilus.

Expression of the Escherichia coli bo-type ubiquinol oxidase with a chimeric subunit II having the CuA-cytochrome c domain from the thermophilic Bacillus caa3-type cytochrome c oxidase

The C-terminal periplasmic domain of subunit II of the Escherichia coli bo-type ubiquinol oxidase was replaced with the counterpart of the thermophilic Bacillus caa3-type cytochrome c oxidase containing the CuA-cytochrome c domain by means of gene engineering techniques. The chimeric terminal oxidase was expressed by a pBR322 derivative in a terminal oxidase deficient mutant of E. coli, although the amount of the chimeric enzyme was smaller than that of the Escherichia coli bo-type ubiquinol oxidase expressed by the original cytochrome bo-expressing plasmid. The chimeric enzyme showed much higher TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine) oxidase activity than the wild-type cytochrome bo, but lower activity than the thermophilic Bacillus caa3-type cytochrome c oxidase. The chimeric subunit II was confirmed to bind to heme C. These results suggest that the CuA-cytochrome c domain grafted to this membrane anchor can facilitate electron transfer from reduced TMPD to low-spin protoheme b in subunit I.

A novel cytochrome b(o/a)3-type oxidase from Bacillus stearothermophilus catalyzes cytochrome c-551 oxidation

Gram-positive thermophilic Bacillus species contain cytochrome caa3-type cytochrome c oxidase as their main terminal oxidase in the respiratory chain. To identify alternative oxidases, we isolated several mutants from B. stearothermophilus defective in the caa3-type oxidase activity [Sakamoto, J. et al (1996) FEMS Microbiol. Lett. 143, 151-158]. A novel oxidase was isolated from membrane preparations of one of the mutants, K17. The oxidase was composed of two subunits with molecular masses of 56 and 19 kDa, and contained protoheme IX, heme O, heme A, and Cu in a ratio of 1:0.7:0.2:3. CO difference spectra indicate that the high-spin heme is mainly heme O. These results suggest that the enzyme belongs to the heme-copper oxidase family and is a cytochrome b(o/a)3-type oxidase, whose high-spin heme is mainly heme O and partly heme A. The enzyme oxidized cytochrome c-551, which is a membrane-bound lipoprotein of thermophilic Bacillus. The turnover rate of the activity (Vmax = 190 s[-1]) and its affinity for cytochrome c-551 (Km = 0.15 microM) were much higher than those for yeast and equine heart cytochromes c. The oxidase activity was enhanced by the presence of salts and inhibited by sodium cyanide with a Ki value of 19 microM. The enzyme kinetics suggests that cytochrome c-551 is the natural substrate to this oxidase. Furthermore, the oxidase had similarity to cytochrome ba3-type oxidase from Thermus thermophilus in the subunit composition, partial amino acid sequence, and prosthetic groups, and therefore is suggested to belong to a unique subgroup of the heme-copper oxidase family together with the Thermus enzyme and archaeal oxidases such as Sulfolobus SoxABCD.

A flash-photolysis study of the reactions of a caa3-type cytochrome oxidase with dioxygen and carbon monoxide

The time course of absorbance changes following flash photolysis of the fully-reduced carboxycytochrome oxidase from Bacillus PS3 in the presence of O2 has been followed at 445, 550, 605, and 830 nm, and the results have been compared with the corresponding changes in bovine cytochrome oxidase. The PS3 enzyme has a covalently bound cytochrome c subunit and the fully-reduced species therefore accommodates five electrons instead of four as in the bovine enzyme. In the bovine enzyme, following CO dissociation, four phases were observed with time constants of about 10 microseconds, 30 microseconds, 100 microseconds, and I ms at 445 nm. The initial, 10-microsecond absorbance change at 445 nm is similar in the two enzymes. The subsequent phases involving heme a and CuA are not seen in the PS3 enzyme at 445 nm, because these redox centers are re-reduced by the covalently bound cytochrome c, as indicated by absorbance changes at 550 nm. A reaction scheme consistent with the experimental observations is presented. In addition, internal electron-transfer reactions in the absence of O2 were studied following flash-induced CO dissociation from the mixed-valence enzyme. Comparisons of the CO recombination rates in the mixed-valence and fully-reduced oxidases indicate that more electrons were transferred from heme a3 to a in PS3 oxidase compared to the bovine enzyme.

Cytochrome bd-type quinol oxidase in a mutant of Bacillus stearothermophilus deficient in caa3-type cytochrome c oxidase

Gram-positive thermophilic Bacillus species contain cytochrome caa3-type cytochrome c oxidase as a terminal oxidase in the respiratory chain. To identify alternative oxidases, we isolated B. stearothermophilus mutants defective in the caa3-type oxidase activity. One mutant contained little cytochrome a and had low cytochrome c oxidase activity. However, growth and the respiratory activity of membranes in the presence of NADH were close to normal, suggesting that the mutant contains an alternative electron transfer pathway. A novel oxidase was isolated from the membrane fraction of the mutant. The enzyme is a cytochrome bd-type quinol oxidase composed of two subunits of 52 and 40 kDa, whose N-terminal regions show sequence similarity to polypeptides of the bd-type oxidase from Escherichia coli and Azotobacter vinelandii. This is the first report of a bd-type terminal oxidase purified from a Gram-positive bacterium.

A cb-type cytochrome-c oxidase terminates the respiratory chain in Helicobacter pylori

A Helicobacter pylori membrane fraction oxidized yeast and equine cytochrome c, and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD). When ascorbate was used as reductant, the Vmax and apparent Km values were 612 nmol electron min-1 (mg protein)-1 and 14 microM for yeast, and 419 nmol electron min-1 (mg protein)-1 and 19 microM for equine cytochrome c, respectively. For TMPD oxidation, the Vmax and Km values were 640 nmol electron min-1 (mg protein)-1 and 182 microM, respectively. These oxidase activities showed a high affinity for oxygen. Inhibition of both cytochrome-c and TMPD oxidase activities by 50% was caused by about 4 microM cyanide and about 0.5 mM azide. Redox difference spectra of the membrane solubilized with Triton X-100 showed b- or c-type cytochromes but not aa3-type cytochromes. c-type and a part of some b-type cytochromes were reduced with ascorbate plus TMPD. A CO difference spectrum revealed that protohaem, but not an aa3-type cytochrome, may be interacting with CO/oxygen. Only protohaem was detected in the haem fraction extracted from the membrane. Three polypeptides (60, 38 and 29 kDa) were found to be bearing haem c after SDS-PAGE of the membrane. From these results, it was suggested that the cbb3-type cytochrome-c oxidase, having a haem-copper binuclear centre like the cytochrome aa3-type oxidase, but differing in a few other properties, functions as a terminal oxidase in the respiratory chain of H. pylori.

Bacillus stearothermophilus qcr operon encoding rieske FeS protein, cytochrome b6, and a novel-type cytochrome c1 of quinol-cytochrome c reductase

The gcr of Bacillus stearothermophilus K1041 encoding three subunits of the quinol-cytochrome c oxidoreductase (cytochrome reductase, b6c1 complex) was cloned and sequenced. The gene (qcrA) for a Rieske FeS protein of 19,144 Da with 169 amino acid residues, and the gene (qcrC) for cytochrome c1 of 27,342 Da with 250 amino acid residues were found at adjacent upstream and downstream sides of the previously reported qcrB (petB) for cytochrome b6 of subunit 25,425 Da with 224 residues (Sone, N., Sawa, G., Sone, T., and Noguchi, S. (1995) J. Biol. Chem. 270, 10612-10617). The three structural genes for thermophilic Bacillus cytochrome reductase form a transcriptional unit. In the deduced amino acid sequence for the FeS protein, the domain including four cysteines and two histidines binding the 2Fe-2S cluster was conserved. Its N-terminal part more closely resembled the cyanobacteria-plastid type than the proteobacteria-mitochondria type when their sequences were compared. The amino acid sequence of cytochrome c1 was not similar to either type; the thermophilic Bacillus cytochrome c1 is composed of an N-terminal part corresponding to subunit IV with three membrane-spanning segments, and a C-terminal part of cytochrome c reminiscent of cytochrome c-551 of thermophilic Bacillus. The subunit IV in the enzyme of cyanobacteria and plastids is the counterpart of C-terminal part of cytochrome b of proteobacteria and mitochondria. These characteristics indicate that Bacillus cytochrome b6c1 complex is unique.

Intra- and inter-complex cross-linking of subunits in the quinol oxidase super-complex from thermophilic Bacillus PS3

Gram-positive thermophilic Bacilli contain quinol-cytochrome c reductase and cytochrome c oxidase as two major respiratory complexes of the electron transfer chain, and these enzymes can be extracted with mild detergents as an associated quinol oxidase super-complex. The reductase is composed of three subunits; cytochrome b6, cytochrome c1, and FeS protein, whereas cytochrome c oxidase consists of four subunits numbered 1 through 4. In order to clarify the interactions between the subunits, the super-complex isolated from Bacillus PS3 was cross-linked with three bifunctional cross-linkers; disuccinimidyl tartrate, 3,3'-dithiobis(succinimidylpropionate), and ethylene glycolbis(sulfosuccinimidylsuccinate). The most prominent cross-linking was observed for the combination of subunit 1 plus 2 in cytochrome c oxidase, and for that of cytochrome b6 plus cytochrome c1 in the reductase. In addition to these intra-complex cross-linkings, inter-complex linking was observed for the combination of cytochrome b6 plus subunit 1 with ethylene glycolbis(sulfosuccinimidylsuccinate), and for the combinations of cytochrome b6 plus subunit 1 and cytochrome b6 plus subunit 2 with 3,3'-dithiobis(succinimidylpropionate). Incubation in the presence of Triton X-100, which was confirmed to cleave the two enzyme complexes, selectively reduced the inter-complex cross-linking, suggesting that the chemical cross-linking reflect the spatial arrangement of subunits in the super-complex.

Nucleotide and amino acid sequences for cytochrome caa3-type oxidase of Bacillus stearothermophilus K1041 and non-Michaelis-type kinetics with cytochrome c

A pseudo-sigmoidal cytochrome c-dependence curve of oxidase activity was observed with cytochrome oxidase from the Bacillus stearothermophilus strain K1041, while the other thermophilic Bacillus PS3 which has been extensively studied possessed normal Michaelis-Menten type kinetics. The genes coding for four subunits of cytochrome caa3-type oxidase and for heme O synthase were isolated from a genomic DNA library of K1041 by using a PS3 DNA fragment containing the highly-conserved region of the largest subunit as a probe, and sequenced. Most residues in subunits I (COI/caaB product), III (COIII/caaC product), and IV (COIV/caaD product) of K1041 were highly conserved when compared with those of PS3. However, the sequence of K1041 subunit II (COII/caaA product) was distinctly different from that of the PS3 subunit II. These Bacillus COIIs have an additional sequence for cytochrome c after the CuA binding protein portion with two transmembrane segments which is homologous to the mitochondrial counterpart, and represents the site of electron ingress. Several charged residues in the vicinity of cytochrome c moiety are replaced by oppositely charged residues. It is likely that these amino acid replacements in subunit II are the cause of the abnormal sigmoidal saturation curve for extrinsic cytochromes c of the K1041 enzyme.

Identification of peptide fragments chemically cross-linked in cytochrome c oxidase from thermophilic Bacillus PS3

In order to study steric arrangement of subunits in cytochrome c oxidase isolated from thermophilic Bacillus PS3, we developed a simple procedure including chemical cross-linking, two consecutive runs of electrophoresis, proteolytic digestion, and peptide sequencing for simultaneous identification of two cross-linked fragments. By this procedure, the cytochrome c domain of subunit 2 was found cross-linked to C-terminal region of subunit 1 including two hydrophobic transmembrane segments, suggesting that these two regions were located close each other. The present simple procedure might be applicable to proteins whose crystal structures are not revealed.

Thermophilic bacilli have split cytochrome b genes for cytochrome b6 and subunit IV. First cloning of cytochrome b from a gram-positive bacterium (Bacillus stearothermophilus)

The genes of Bacillus stearothermophilus K1041 encoding cytochrome b(6) (Bacillus cytochrome b is referred to as cytochrome b(6) for its resemblance to plastid b6) and subunit IV of the quinol:cytochrome c oxidoreductase (bc1 complex) were cloned and sequenced. For preparation of the probe for cloning, polymerase chain reaction was carried out using oligonucleotide mixtures targeting for N-terminal regions of cytochrome bc and subunit IV of the thermophilic Bacillus PS3. The deduced amino acid sequences contained 224 residues of 25,425 daltons for cytochrome b(6) and 173 residues of 19,371 daltons for subunit IV, and both open reading frames were separated by 67 base pairs. Cytochrome b and subunit IV contained 4 and 3 hydrophobic transmembrane segments, respectively, indicating that the fourth segment of subunit IV (eighth segment of cytochrome b) is lacking. Four histidine residues supposed to ligand two protohemes were conserved, but the two His in the fourth segment were separated by 14 amino acid residues like cytochrome b6, not like mitochondrial cytochrome b. The residues that might have conferred the two quinol-binding sites were mostly conserved, but especially the third His residue in the fourth segment of mitochondrial cytochrome b was replaced by Arg in Bacillus cytochrome b6 as in cytochrome b6. These characteristics and quantitative comparison of the protein sequences indicate that this Bacillus sequence is unique and meanwhile rather close to the cyanobacteria-plastids type than the purple bacteria-mitochondria type.

Preparation and characterization of the hydrophilic CuA-cytochrome c domain of subunit II of cytochrome c oxidase from thermophilic bacillus PS3

Cytochrome c oxidase of the thermophilic bacterium, PS3, was treated with trypsin. The hydrophilic domain of 26 kDa can be easily cleaved off from the hydrophobic anchor domain at the N-terminal region of subunit II, but remains attached to the rest of the enzyme upon gel-filtration in the presence of 0.2% lauroyl sarcosinate. The separation occurred in the presence of 5 M urea in addition to 0.2% lauroyl sarcosinate. After relatively prolonged proteolysis, that induced severe activity decay, and subunit I fragmentation, the 26 kDa fragment of subunit II can be easily isolated from the rest, suggesting that this fragment with cytochrome c and CuA interacts with subunit I. The separated fragment showed absorption spectra due to CuA and cytochrome c. Reconstitution of the cytochrome oxidase activity occurred on addition of the 26 kDa fragment to the proper gel-filtration chromatographic fraction.

Kinetics of platelets in dogs with thrombocytopenia induced by antiglycoprotein IIb/IIIa receptor monoclonal antibody

To experimentally assess the kinetics of platelets in thrombocytopenia, we constructed a canine model using 111In-oxine labeled autologous platelets and an intact antiplatelet monoclonal antibody (MAb) NNKY2-11 (IgG2a). With the infusion of radiolabeled autologous platelets into dogs, the peripheral platelet count and blood radioactivity level were examined, and the radioactivity in the liver, spleen and heart was determined with scintigraphic analysis. Thereafter, i.v. injection of 100 micrograms/kg of NNKY2-11 had no effect on platelet counts or the biodistribution of radiolabeled platelets. However, 200 and 300 micrograms/kg of MAb reduced the platelets, and the radioactivity of the liver and spleen augmented clearly after injection of MAb. Platelet radioactivity in serum, which had decreased after MAb infusion, did not recover, even when peripheral platelet counts returned to the normal levels, indicating that these new platelets might be derived from the platelet-storage pool or new thrombocytogenesis. This model of antiplatelet MAb induced thrombocytopenia seems to be useful for analyzing the kinetics of platelets in thrombocytopenia.

Over-expression of membrane-bound cytochrome c-551 from thermophilic Bacillus PS3 in Bacillus stearothermophilus K1041

Cytochrome c-551 is a lipoprotein of about 10500 Da, found in thermophilic Bacillus PS3 grown under air-limited conditions. An expression vector was constructed from a structural gene of PS3 cytochrome c-551, synthetic oligonucleotide as a promoter for Bacillus stearothermophilus and a shuttle vector for Escherichia coli and B. stearothermophilus. The transformed cells of B. stearothermophilus K1041 expressed cytochrome c-551 as much as 5 nmol/mg membrane protein. The effects of over-expression on the host cells are analyzed; a slightly slower growth rate and an increased synthesis of cytochrome oxidase (about twofold) occurred. Over-expressed (4-10-fold) cytochrome c-551 were purified and its properties were examined to know whether the protein is processed as in PS3 cells grown under air-limited conditions. The molecular mass determination and treatment with Rhizopus lipase suggested that the same processes, cleavage of signal peptidase, blocking of the N-terminal group and acylation of glycerol residue by two fatty acids, took place in the over-expression system. Fatty acylation seems useful for the cytochrome c to be effectively oxidized.

Membrane-bound Bacillus cytochromes c and their phylogenetic position among bacterial class I cytochromes c

Gram-positive bacteria lack a periplasmic compartment and contain only membrane-bound cytochromes c. There are at least two types. One is found in subunit II of cytochrome oxidase, and the other is small cytochrome c which is also membrane-bound because of an unprocessed signal sequence or post-translational acylation at the N-terminal end of the protein. These Bacillus cytochromes c are compared with known class I cytochromes c, and a phylogenetic tree has been constructed by the neighbour-joining method.

Proton pumping activity and visible absorption and resonance Raman spectra of a cao-type cytochrome c oxidase isolated from the thermophilic bacterium Bacillus PS3

Cytochrome c oxidase having heme O in addition to heme C and heme A (cytochrome cao) [Sone, N., & Fujiwara, Y. (1991) FEBS Lett. 288, 154-158] was isolated from a thermophilic bacterium, Bacillus PS3, grown under slightly air-limited conditions. Cytochrome cao could oxidize yeast cytochrome c and N,N,N',N'-tetramethyl-p-phenylenediamine twice as fast as cytochrome caa3, which this organism yielded under normal growing conditions. Cytochrome cao also pumped protons upon cytochrome c oxidation in a way similar to cytochrome caa3. Binding of cyanide to cytochrome cao caused spin-state conversion of heme O at the binuclear center and seriously inhibited its physiological activity. A low Ki value (0.4 microM) for cyanide was found to be mainly due to a small "off" constant. Resonance Raman spectra of cytochrome cao bore close resemblance to those of cytochrome caa3 in both oxidized and reduced states, although the formyl stretching (vCH=O) band was absent. The Fe-histidine stretching (vFe-His) and Fe-CO stretching (vFe-CO) frequencies of cytochrome cao were very close to those seen for cytochrome caa3, but were distinct from those of hemoglobin and peroxidases, suggesting that the protein structure in the vicinity of heme O resembles that of the heme a3 moiety of cytochrome caa3.

The genes in the thermophilic cyanobacterium Synechococcus vulcanus encoding cytochrome-c oxidase

It is still controversial whether cyanobacteria (blue-green algae) contain an aa3-type cytochrome-c oxidase. We have approached this problem using DNA analysis. Using a DNA probe coding for the most conserved part of subunit I of the Bacillus enzymes, structural genes for the oxidase of a thermophilic cyanobacterium Synechococcus vulcanus were cloned and sequenced. We found genes for subunits II, I, III and IV of this order like those of the Bacillus enzymes, and a terminator structure after the gene for subunit IV. The deduced protein sequences for the subunits II, I and III showed consensus amino-acid residues atevery important portion, suggesting that these genes are operating. However, the S. vulcanus oxidase lacked a cytochrome-c-moiety fused to subunit II, the 13th and 14th hydrophobic segments of subunit I which are lacking in the Paracoccus enzyme, and the 1st and 2nd ones of subunit III which are lacking in the Bacillus enzyme, were not found. A gene homologous to ctaB gene, which locates at the 5'-upstream region of the gene for subunit II and co-transcribed in Bacillus subtilis, was not found. Comparison of protein sequences showed that S. vulcanus cytochrome oxidase is closer to Bacillus cytochrome oxidases than the mitochondrial and Paracoccus enzymes, or quinol oxidases from B. subtilis and Escherichia coli.

Cytochrome c-551 of the thermophilic bacterium PS3, DNA sequence and analysis of the mature cytochrome

The structural gene for cytochrome c-551 was isolated from genomic DNA of the thermophilic bacterium PS3. The amino acid sequence of cytochrome c-551 as deduced from the DNA sequence consists of 111 amino acid residues and contains one heme c-binding site (-CASCH-) located approximately in the middle of the polypeptide. The N-terminus of isolated cytochrome c-551 was blocked, but treatment with Rhizopus lipase and molecular weight measurement of the mature and lipase-treated forms by ion spray mass spectroscopy suggest that the mature c-551 may have 93 or 94 amino acid residues with a diacylated glycerol-cysteine at the N-terminal region. The first 17 or 18 amino acid residues in the N-terminal region of the nascent polypeptide, rich in hydrophobic and basic amino acid residues, may be a signal peptide to translocate the major portion of cytochrome c-551 to the extracellular surface and to be processed. Similarity of amino acid sequence of this protein is discussed in relation to other c-type cytochromes of bacilli as well as bacterial small cytochromes c such as Pseudomonas aeruginosa cytochrome c-551 and cytochrome c6 of cyanobacteria.

Effects of aeration during growth of Bacillus stearothermophilus on proton pumping activity and change of terminal oxidases

The effects of aeration during bacterial growth on the proton translocating activity of the respiratory chain of B. stearothermophilus ATCC 8005, which is stable enough for measurement of the H+/O ratio by an oxygen pulse method, were examined. For endogenous and ascorbate-N,N,N',N'-tetramethyl p-phenylene diamine (TMPD) respiration, H+/O ratios of around 6 and 2 were obtained using resting cells grown under highly aerated conditions. The values were about 4 and 0 when cells were grown under limited-air conditions. Spectrophotometric and enzyme kinetical analyses revealed that both cytochrome caa3 and pigment-432 (cytochrome cao) were acting as terminal oxidases, while cytochrome b-558 (corresponding to the "cytochrome o-type oxidase" of the thermophilic bacterium PS3 in the previous paper [Sone, N., Kutoh, E., & Sato, K. (1990) J. Biochem. 107, 597-602]) was mainly serving in the cells grown under limited-air conditions. Measurement of the pH change upon ferrocytochrome c pulse with proteoliposomes reconstituted from the membrane extract of vigorously aerated cells and that of limited-air cells suggested that both cytochrome caa3, and pigment-432 (cytochrome cao) pump protons, while cytochrome b-558 does not.

The cytochrome C oxidase genes in blue-green algae and characteristics of the deduced protein sequence for subunit II of the thermophilic cyanobacterium Synechococcus vulcanus

Blue-green algae (cyanobacteria) contain both primitive photosynthetic and respiratory systems in their membranes. The controversial genes coding for an alpha alpha 3-type cytochrome oxidase in cyanobacteria were examined. The DNA probe coding for the most conserved part of subunit I hybridized with DNA fragments from four cyanobacterial species. We have cloned the genes coding for subunits I and II from the genomic library of the thermophilic cyanobacterium Synechococcus vulcanus and determined the nucleotide sequence of the subunit II gene. The deduced protein sequence (327 amino acid residues) indicates that there are two hydrophobic segments near the N-terminus and a hydrophilic intermembrane domain containing ligands for CuA (the ESR-active Copper) similar to other subunit IIs. The S. vulcanus subunit II does not contain the cytochrome c moiety that is present in bacilli and thermophiles.

Haem O2 can replace haem A in the active site of cytochrome c oxidase from thermophilic bacterium PS3

Thermophilic bacterium PS3 cultured under slightly air-limited conditions showed a mitochondrion-like cytochrome pattern similar to that in vigorously aerated cells, but an o-type cytochrome replaced cytochrome a3 as the CO-binding centre. Cytochrome cao-type oxidase was purified from the cell membranes by almost the same procedure as used for cytochrome caa3. The turnover number of cytochrome cao was higher than that of cytochrome caa3, but the Km's of the two enzymes for cytochrome c and O2 were almost the same. Gel electrophoresis in the presence of sodium dodecyl sulfate gave bands of four subunits at the identical positions both for cytochrome cao and cytochrome caa3. Cytochrome cao contained a novel kind of haem in addition to haems C and A. This novel haem is likely to be haem O, very recently found as the chromophore of the cytochrome bo complex in Escherichia coli. These data suggest that cytochrome cao is an alternative form of cytochrome c oxidase (cytochrome caa3), in which the cytochrome a3 centre of the enzyme is replaced with cytochrome o.

Synergistic action in platelet activation induced by an antiplatelet autoantibody in ITP

We detected an autoantibody which activated normal platelets in a patient with immune thrombocytopenic purpura and investigated the mechanism by which this autoantibody mediated platelet activation. The patient's IgG induced platelet aggregation and ATP secretion in normal platelet-rich plasma (PRP). IgG-induced aggregation was inhibited by aspirin (ASA), apyrase, a protein kinase C (PKC) inhibitor and two anti-platelet glycoprotein (GP) IIb/IIIa monoclonal antibodies. The increase of aequorin-detected intraplatelet Ca2+ induced by the patient's IgG was extremely slight. Phosphorylation of a 40 kDa protein was induced by the patient's IgG without any obvious phosphorylation of a 20 kDa protein, and was inhibited by a PKC inhibitor but not by ASA. With ASA-treated normal PRP, the patient's IgG failed to induce aggregation itself, but enhanced ADP- or STA2-induced aggregation. Western blotting and immunoprecipitation experiments showed that the patient's IgG reacted to a protein of 36 kDa. These results suggest that the platelet activation induced by this autoantibody depended on both the selective activation of PKC and the slight Ca2+ mobilization induced by thromboxane A2 synthesis, while the aggregation depended on secretion induced by the synergistic action of the above two mechanisms and was mediated through GP IIb/IIIa.